An abdominal or thoracic aortic aneurysm is a condition in which a portion of the aorta wall is weakened and expands over time, thereby forming an aneurysmal sac. At some point, the aneurysmal sac may rupture and cause major bleeding. Patients with a ruptured aneurysm have a very high mortality rate. Modern imaging techniques allow for early diagnosis of an aneurysm. Early diagnosis, along with an aging population, may increase the number of patients diagnosed with an aneurysm over the coming years.
Aneurysms may be surgically excised and replaced with a synthetic graft when the aneurysmal sac reaches a diameter of approximately five centimeters in diameter. The surgical resection of an aneurysm is highly durable but also highly invasive. The patient typically stays in the hospital for a few days and recovers at home for a month or longer. Surgical resection of an aneurysm can result in various complications.
The endovascular repair of aneurysms has been developed. During this procedure, an expandable stent/graft is deployed with an endoscope. The deployed stent/graft spans the aneurysmal sac and overlaps with healthy portions of the aorta; successful insertion of a stent/graft excludes the aneurysmal sac from exposure to aortic blood pressure, and a thrombus forms in the sac over time. This approach is less-invasive than traditional resection; the hospital stay is shortened and recovery is faster. Endovascular repair can be performed on some patients who cannot undergo a traditional surgery due to age limitations or for other reasons.
Failure of the stent/graft to completely exclude the aneurysm from aortic blood pressure may result in continued pressurization of the aneurysmal sac, and may result in eventual rupture and bleeding. There are several factors that may result in aneurysmal sac pressure after stent/graft implantation. These include graft-related factors—such as the presence of endoleaks, graft porosity, and graft compliance—as well as anatomic factors, such as continuing patency of the aneurysm side branches, misfit of the stent/graft to the aorta, the aneurysm morphology, and characteristics of the aneurysm thrombus. Endoleaks—persistent perfusion of the aneurysmal sac—are variously reported to result in anywhere from 10% to 50% of cases.